Leprosy, also known as Hansen disease, is a chronic infectious disease caused mainly by a type of bacteria called Mycobacterium leprae. The disease affects the skin, the peripheral nerves, the mucosa of the upper respiratory tract and the eyes. Apart from the physical deformity, persons affected by leprosy also face stigmatization and discrimination. However, leprosy is curable and treatment in the early stages can prevent disability.

The disease is believed to be transmitted through inhalation of droplets from the nose and mouth of an untreated case of leprosy, containing the causative agent, following prolonged, close contact. The disease does not spread through casual contact (like shaking hands or hugging, sharing meals, or sitting next to each other). The patient stops transmitting the disease upon initiation of treatment.

Symptoms may occur within one year of being infected but can also take as long as 20 years or even more. The disease manifests commonly through skin lesion and peripheral nerve involvement.

Skin lesion usually has a different pigmentation than the surrounding normal skin (less pigmented or reddish) and may have various presentations (flat, raised or nodules). Skin lesion can be single or multiple with a definite loss of sensation.

Leprosy is a highly variable disease, affecting people in different ways, according to their immune response.

The diagnosis of leprosy is done clinically. Laboratory-based services may be required in cases that are difficult to diagnose. The diagnosis of leprosy is based on at least one of the following cardinal signs: (i) definite loss of sensation in a pale (hypopigmented) or reddish skin patch; (ii) thickened or enlarged peripheral nerve, with loss of sensation and/or weakness of the muscles supplied by that nerve; (iii) microscopic detection of bacilli in a slit-skin smear. Based on the above, cases of leprosy are classified into two types for treatment purposes: a paucibacillary (PB) case or a multibacillary (MB) case.

PB case: a case of leprosy with 1–5 skin lesions, without demonstrated presence of bacilli in a skin smear.

MB case: a case of leprosy with more than five skin lesions; or with nerve involvement (pure neuritis, or any number of skin lesions and neuritis); or with the demonstrated presence of bacilli in a slit-skin smear, irrespective of the number of skin lesions.

Leprosy is a curable disease. The currently recommended treatment regimen consists of three medicines (dapsone, rifampicin and clofazimine) and is referred to as multidrug therapy (MDT). The same regimen with a duration of 6 months for PB and 12 months for MB cases has been recommended by WHO.

MDT kills the pathogen and cures the patient. Early diagnosis and prompt treatment can help to prevent disabilities.

WHO has been providing MDT free of cost. Free MDT was initially funded by The Nippon Foundation (TNF) and has been donated by Novartis since 2000. 

Recommended treatment regimens